COVID-19 Demonstrates Higher Symptom Frequency than Influenza

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Post-COVID symptoms represent a significant public health burden due to their frequency and duration. As COVID-19 becomes endemic, investigators say the long-lasting effects of the disease should not be overlooked or underestimated.

A recent study emphasizes the need for ongoing research and the development of effective treatments for those experiencing post-viral symptoms, particularly following COVID-19.

“Post-viral symptoms have long been known in the medical community, but more recently received public attention due to the COVID-19 pandemic,” wrote a team of investigators led by Falko Tesch, MSc, associated with the Dresden University of Technology, in Germany. “Post-COVID condition include a wide variety of post-viral symptoms and conditions resulting from SARS-CoV-2 infection that affect many people worldwide, even after the pandemic has ended. Although several clinical trials are currently underway, there are currently no approved therapies for patients with post-COVID condition.”

Eligible patients included in the analysis completed a six-month follow-up questionnaire in addition to at least one other questionnaire at either 12 months or 18 months.

Most COVID symptoms and conditions resolve within one year from diagnosis, although any long-term symptoms have the potential to severely impact the activities of daily life. A recent study revealed Long-COVID caused approximately 80.4 disability-adjusted life years per 1,000 patients for those who were not hospitalized and 642.8 life years among those who were hospitalized. The estimations of prevalence from patients enrolled in the studies are difficult to identify due to variances in follow-up periods, data collection tools and study designs.

This current study explored the long-term effects of post-viral symptoms in individuals who had COVID-19 compared to those who had influenza or no infection at all.

Results revealed individuals who experienced COVID-19 often reported symptoms that persisted long after their initial infection, commonly known as "Long COVID." However, there has been limited data on how these long-lasting symptoms compare to those caused by other viral infections like the flu.

Data was analyzed from a large population-based cohort of 573,791 people living in Germany who had a confirmed COVID-19 infection in 2020. These people were matched against two groups of controls: one from contemporary times who had no COVID-19 infection, and another from the 2018 influenza outbreak. The follow-up period extended up to 18 months after the initial infection to determine how long post-viral symptoms persisted in both the COVID-19 and flu cohorts.

Results demonstrated that people who had COVID-19 were more likely to experience post-viral symptoms compared with those who had influenza or had no infection. These symptoms included fatigue, cognitive issues, difficulty breathing and tissue damage, among other long-term effects. While both COVID-19 and influenza patients experienced symptoms that lingered for months, COVID-19 patients reported these issues more frequently and with higher severity.

The analysis demonstrated that the persistence of post-viral symptoms was similarly long-lasting between COVID-19 and flu patients, but COVID-19 led to these complications more often.

Investigators said Long-COVID can present as either tissue damage and symptoms or conditions due to the chronic stimulation of the immune system. Chronic immune system stimulation symptoms included cognitive problems, fatigue and respiratory issues.

“After one year, only a minority of the initial patients still suffer from post-COVID condition with a similar pattern of persistence among patients with influenza,” investigators said. “However, given the increasingly endemic nature of the disease people will be infected every season, resulting in a constant patient population that needs care.”